Method for preparing vaccine for dental caries and vaccinal compositions for dental caries used as nasal drop

ABSTRACT

A method for preparing a vaccine for dental caries comprises the step of culturing a variant which is obtained by integrating a protein antigen (PAc)-expressing gene into the chromosomal gene of a Streptococcus mutans GS-5 strain to obtain the protein antigen, the protein antigen being produced on the surface of cells of oral Streptococcus mutans or it being extracellularly produced by the microorganism and having a molecular weight ranging from about 170,000 to 220,000. Streptococcus mutans GS-5 (K-3), in which a protein antigen-expressing gene is integrated into the chromosomal gene thereof, has an ability of producing the protein antigen on the surface of the cells or extracellularly. A preventive vaccine composition for dental caries for nasal drops comprises the protein antigen thus produced by the strain: Streptcoccus mutans, the vaccine being intranasally administered. The method makes it possible to enhance the yield of PAc and to simplify processes for purifying PAc. The vaccine composition makes-it possible to internally easily absorb the protein antigen, PAc, in high efficiency and it also makes it possible to effectively increase the antibody titer observed after the administration thereof.

BACKGROUND OF THE INVENTION

The present invention relates to a method for preparing a vaccine for dental caries, a novel variant of Streptococcus mutans GS-5 as well as a vaccinal composition for dental caries which is used as nasal drops.

Streptococcus mutans group is the most crucial pathogenic factor in dental caries in human beings and animals. The S. mutans group is divided into 7 species depending on the characteristics of their DNA's and S. mutans of serotype c, which is most closely related to human dental caries, posesses, on its surface, substances having various antigenicities such as serotype-specific polysaccharide antigens, lipoteichoic acid and protein antigens.

One of these substances present on the bacterial cell surface, a protein antigen having a molecular weight of about 190,000 determined by SDS polyacrylamide gel electrophoresis, is a fine fibrous structure called fimbriae. This protein antigen is known variously as I/II, B, P1 and IF and it does not yet have a uniform name. Thus, this protein antigen is herein called PAc (protein antigen serotype c).

The protein antigen of S. mutans has thus come to atract much interest in connection with development of a vaccine for dental caries. For instance, Japanese Patent Un-examined Published Application (hereunder referred to as "J.P. KOKAI") No. Sho 56-501362 proposes the use of the antigen I/II posessing specific properties as a vaccine for dental caries and J.P. KOKAI No. Sho 58-164518 discloses a vaccine for preventing the decay of teeth. The vaccine comprises, as an antigen, the component of bacterial cells of microorganisms belonging to genus Streptococcus or an extract thereof.

However, even if S. mutans is cultured in 10 liters of a culture medium and PAc is extracted therefrom, only several mg of PAc can be recovered. Thus, this technique cannot be put to practical use. In addition, the purification process for removing impurities from the resulting culture medium requires a great deal of labor and time since the concentration of PAc in the culture medium is very low.

Under such circumstances, the inventors of this invention have tried to insert a PAc-expressing gene(pac gene) of S. mutans into a host such as E. coli (Escherichia coli) or S. milleri (a species of Streptococcus) to thus make the host cells produce rPAc. However, no increase in yield was achieved because the gene was integrated into the bacteria of different species and rPAc was not externally secreted. In this respect, the term "rPAc" herein means PAc obtained through gene recombination (recombinant PAc) and it is a protein having a structure substantially identical with that of PAc.

Moreover, the inventors linked the pac gene to a plasmid-shuttle vector which can proliferate in both E. coli and Streptococcus host cells and inserted it into a S. mutans GS-5 strain which cannot express PAc. The results are reported in Review of Nippon Dentistry Society, 1989, No. 555. However, this method suffers from various problems. For instance, after insertion of the pac gene into the cells of the GS-5 strain, it is sometimes observed that the plasmid carrying the gene is left out of the resulting recombinant bacterial cells and thus the variant stops the production of PAc and the products are insufficient in their uniformity.

On the other hand, there have been known a protective vaccine for dental caries which contains the foregoing protein antigen, i.e., PAc and the vaccine has been used through injection or oral administration.

However, if immunization is carried out by injection via skin, muscle or veins, local inflammation or even functional disorders may possibly be caused. In addition, since the injection is accompanied by pain, it is difficult to immunize an infant or a child through injection and patients are in general reluctant to have a vaccine injected at certain portions such as, for instance, near the parotid. Furthermore, it is difficult to increase the antibody titer in saliva by the administration through injection.

Moreover, if it is orally administered, it may be digested in the stomach. Also, oral administration is liable to causes immune tolerance and consequent loss of response to the corresponding antigen. Besides, a high antibody titer cannot be achieved by the oral immunization.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for preparing a vaccine for dental caries which makes it possible to enhance the yield of PAc and to simplify processes for purifying PAc as well as a variant of S. mutans GS-5 in which a pac gene is integrated into its chromosomal gene.

Another object of the present invention is to provide a vaccine composition whose component, the protein antigen PAc, is internally easily absorbed, in high efficiency, by a subject for immunization.

A further object of the present invention is to provide a vaccine composition capable of effectively increasing the antibody titer in a subject for immunization after the administration thereof and capable of sufficiently showing its vaccination effect.

These and other objects of the present invention will be apparent from the following description and Examples.

The method for preparing a vaccine for dental caries comprises the step of culturing a variant of an S. mutans GS-5 strain in which a protein antigen (PAc)-expressing gene (pac gene) is integrated into its chromosomal gene, the pac gene being produced on the surface of cells of oral Streptococcus mutans or it being extracellularly produced by the microorganism and having a molecular weight ranging from about 170,000 to 220,000.

The novel strain (Streptococcus mutans GS-9 (K-3) strain; FERM BP-2437) of the present invention was established through genetic engineering. More specifically, it was established by integrating the pac gene into the chromosomal gene of host cells, oral Streptococcus: Streptococcus mutans, to transform the host cells to thus substantially improve their productivity of PAc. The strain Streptococcus mutans GS-5 (K-3) was deposited as FERM BP-2437 at the Fermentation Research Institute in Japan on May 24, 1989.

The preventive vaccine for dental caries of the present invention comprises the protein antigen (PAc) which is produced on the surface of the cells of oral Streptococcus mutans or extracellularly produced by the microorganism. The composition is used in the form of a nasal drop which is intranasally applied.

The preventive vaccine for dental caries for nasal drop may further comprise a surfactant, cholera toxin B subunit or a bile acid or a derivative thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating the result of agarose electrophoresis of a plasmid-containing fraction. In the electrophoresis diagram, lane 1 illustrates the plasmid pSM1 (cyclic plasmid): lane 2 illustrates the plasmid-containing fraction of the GS-5 strain; lane 3 illustrates the plasmid-containing fraction of GS-5 (K-3) strain; and lane 4 illustrates the plasmid-containing fraction of GS-5 (K-9) strain.

FIG. 2 is a diagram for showing the results of the Southern blot analysis of a chromosomal DNA using a ³² P-labeled erythromycin-resistant gene, Bam HI fragment, as a probe. In the Southern blot analysis, lane 1 represents the Eco RI fragment of chromosomal DNA of the GS-5 strain; lane 2 represents the Eco RI fragment of chromosomal DNA of the GS-5 (K-3) strain; and lane 3 represents the Eco RI fragment of chromosomal DNA of the GS-5 (K-9) strain.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, the S. mutans GS-5 strain is employed as host bacteria, while any donor bacteria may be used so far as they are strains belonging to species S. mutans capable of producing PAc and preferred are, for instance, strains of c serotype, e serotype and f serotype. Thus, optimum suppression of change in the structure of the rPAc produced can be realized by selecting host and donor bacteria from those belonging to the same species.

The S. mutans GS-5 strain is a known strain of S. mutans which is incapable of producing PAc and is preserved at various research institutes such as universities. The applicant of this invention deposited it with the Fermentation Research Institute (FRI) under an accession number of FERM BP-2436 under a designation of Streptococcus mutans GS-5 strain so that a third party can easily obtain it. The strain Streptococcus mutans GS-5 strain was deposited as FERM BP-2436 at the Fermentation Research Institute in Japan on May 24, 1989.

Examples of the donor bacteria used in the present invention include Streptcoccus mutans NCTC 10449, Streptococcus mutans MT8148, Streptococcus mutans Ingbritt, Streptococcus mutans MT6, Streptococcus mutans JC2, Streptococcus mutans MT118, Streptococcus mutans C67-1, Streptococcus mutans OMZ70, Streptococcus mutans MT6801, Streptococcus mutans JC 1-5, Streptococcus mutans ATCC 33477, Streptococcus mutans SE11, Streptococcus mutans OMZ175, Streptococcus mutans MT557, Streptococcus mutans P2 and Streptococcus mutans PK-1.

With the use of such donor bacteria, a gene which encodes PAc is inserted into the chromosome of the Streptococcus mutans GS-5 strain in a manner conventionally known in the art and thus the Streptococcus mutans GS-5 (K-3) strain of the present invention can be obtained. In this process, as the vector (plasmid for transferring PAc), there may be used, for instance, shuttle vectors pSA3 and pVA981 and as restriction enzymes for cleavage, there may be used, for instance, Bam HI, Sph I, Bgl II, Eco RI, Eco T14I, Hind III, Pst I and Sac I.

In the present invention, examples of the genes which encode the protein antigen (PAc) having a molecular weight ranging from about 170,000 to 220,000 preferably 180,000 to 210,000, include base sequences which encode the fragment substantially comprising 1,565 amino acid residues from the initiation codon (ATG) to the termination codon (TGA) of the following base sequence and fragments thereof. In addition, it is also possible to use base sequences in which a part thereof is replaced with other bases or one or more of the bases are deleted and which exhibit antigenicity substantially identical with that of PAc.

       T TTG TGC TTT AGA ATT AAT GTT GGA TAA AGT GTG GAG TTT GTC CTC  46   47      GAA AAA TAG CAG CGA TTG AAT GTG TTT ATA ATT CTG ATT CAG ACA TTA  94   95      GTT TTT ATT TCA GCA AAA ATT GAC AAA TCA AAT CAA TTA TAT TAC AAT  142      143 TTT TTA ACG TAT ATT ACA AAA ATA TAT TTG GAA GAT TTA TTC AGA TTT  190        191 GGA GGA TTT ATG AAA GTC AAA AAA ACT TAC GGT TTT CGT AAA AGT AAA      238     Met Lys Val Lys Lys Thr Tyr Gly Phe Arg Lys Ser Lys  13   239      ATT AGT AAA ACA CTG TGT GGT GCT GTT CTA GGA ACA GTA GCA GCA GTC  286  14      Ile Ser Lys Thr Leu Cys Gly Ala Val Leu Gly Thr Val Ala Ala Val  29      287 TCT GTA GCA GGA CAA AAG GTT TTT GCC GAT GAA ACG ACC ACT ACT AGT  334       30 Ser Val Ala Gly Gln Lys Val Phe Ala Asp Glu Thr Thr Thr Thr Ser  45       335 GAT GTA GAT ACT AAA GTA GTT GGA ACA CAA ACT GGA AAT CCA GCG ACC      382  46 Asp Val Asp Thr Lys Val Val Gly Thr Gln Thr Gly Asn Pro Ala Thr      61   383 AAT TTG CCA GAG GCT CAA GGG AGT GCG AGT AAG GAA GCT GAA CAA ACT       430  62 Asn Leu Pro Glu Ala Gln Gly Ser Ala Ser Lys Glu Ala Glu Gln Ser       77   431 CAA ACC AAG CTG GAG AGA CAA ATG GTT CAT ACC ATT GAA GTA CCT      AAA  478  78 Gln Thr Lys Leu Glu Arg Gln Met Val His Thr Ile Glu Val Pro      Lys  93   479 ACT GAT CTT GAT CAA GCA GCA AAA GAT GCT AAG TCT GCT GGT      GTC AAT  526  94 Thr Asp Leu Asp Gln Ala Ala Lys Asp Ala Lys Ser Ala Gly      Val Asn  109   527 GTT GTC CAA GAT GCC GAT GTT AAT AAA GGA ACT GTT AAA      ACA CCT GAA  574  110 Val Val Gln Asp Ala Asp Val Asn Lys Gly Thr Val      Lys Thr Pro Glu  125   575 GAA GCA GTC CAA AAA GAA ACT GAA ATT AAA GAA      GAT TAC ACA AAA CAA  622  126 Glu Ala Val Gln Lys Glu Thr Glu Ile Lys      Glu Asp Tyr Thr Lys Gln  141   623 GCT GAG GAT ATT AAG AAG ACA ACA GAT      CAA TAT AAA TCG GAT GTA GCT  670  142 Ala Glu Asp Ile Lys Lys Thr Thr      Asp Gln Tyr Lys Ser Asp Val Ala  157   671 GCT CAT GAG GCA GAA GTT GCT      AAA ATC AAA GCT AAA AAT CAG GCA ACT  718  158 Ala His Glu Ala Glu Val      Ala Lys Ile Lys Ala Lys Asn Gln Ala Thr  173   719 AAA GAA CAG TAT GAA      AAA GAT ATG GCA GCT CAT AAA GCC GAG GTT GAA  766  174 Lys Glu Gln Tyr      Glu Lys Asp Met Ala Ala His Lys Ala Glu Val Glu  189   767 CGC ATT AAT      GCT GCA AAT GCT GCC AGT AAA ACA GCT TAT GAA GCT AAA  814  190 Arg Ile      Asn Ala Ala Asn Ala Ala Ser Lys Thr Ala Tyr Glu Ala Lys  205   815 TTG      GCT CAA TAT CAA GCA GAT TTA GCA GCC GTT CAA AAA ACC AAT GCT  862  206      Leu Ala Gln Tyr Gln Ala Asp Leu Ala Ala Val Gln Lys Thr Asn Ala  221      863 GCC AAT CAA GCA GCC TAT CAA AAA GCC CTT GCT GCT TAT CAG GCT GAA  910       222 Ala Asn Gln Ala Ala Tyr Gln Lys Ala Leu Ala Ala Tyr Gln Ala Glu      237   911 CTG AAA CGT GTT CAG GAA GCT AAT GCA GCC GCC AAA GCC GCT TAT      GAT  958  238 Leu Lys Arg Val Gln Glu Ala Asn Ala Ala Ala Lys Ala Ala      Tyr Asp  253   959 ACT GCT GTA GCA GCA AAT AAT GCC AAA AAT ACA GAA ATT      GCC GCT GCC 1006  254 Thr Ala Val Ala Ala Asn Asn Ala Lys Asn Thr glu      Ile Ala Ala Ala  269  1007 AAT GAA GAA ATT AGA AAA CGC AAT GCA ACG GCC      AAA GCT GAA TAT GAG 1054  270 Asn Glu Glu Ile Arg Lys Arg Asn Ala Thr      Ala Lys Ala Glu Tyr Glu  285  1055 ACT AAG TTA GCT CAA TAT CAA GCT GAA      CTA AAG CGT GTT CAG GAA GCT 1102  286 Thr Lys Leu Ala Gln Tyr Gln Ala      Glu Leu Lys Arg Val Gln Glu Ala  301  1103 AAT GCC GCA AAC GAA GCA GAC      TAT CAA GCT AAA TTG ACC GCC TAT CAA 1150  302 Asn Ala Ala Asn Glu Ala      Asp Tyr Gln Ala Lys Leu Thr Ala Try Gln  317  1151 ACA GAG CTT GCT CGT      GTT CAA AAA GCC AAT GCG GAT GCT AAA GCG ACC 1198  318 Thr Glu Leu Ala      Arg Val Gln Lys Ala Asn Ala Asp Ala Lys Ala Thr  333  1199 TAT GAA GCA      GCT GTA GCA GCA AAT AAT GCC AAA AAT GCG GCA CTC ACA 1246  334 Tyr Glu      Ala Ala Val Ala Ala Asn Asn Ala Lys Asn Ala Ala Leu Thr  349  1247 GCT      GAA AAT ACT GCA ATT AAG CAA CGC AAT GAG AAT GCT AAG GCG ACT 1294  350      Ala Glu Asn Thr Ala Ile Lys Gln Arg Asn Glu Asn Ala Lys Ala Thr  365      1295 TAT GAA GCT GCA CTC AAG CAA TAT GAG GCC GAT TTG GCA GCG GTG AAA      1342  366 Tyr Glu Ala Ala Leu Lys Gln Tyr Glu Ala Asp Leu Ala Ala Val      Lys  381  1343 AAA GCT AAT GCC GCA AAC GAA GCA GAC TAT CAA GCT AAA TTG      ACC GCC 1390  382 Lys Ala Asn Ala Ala Asn Glu Ala Asp Tyr Gln Ala Lys      Leu Thr Ala  397  1391 TAT CAA ACA GAG CTC GCT CGC GTT CAA AAA GCC AAT      GCG GAT GCT AAA 1438  398 Tyr Gln Thr Glu Leu Ala Arg Val Gln Lys Ala      Asn Ala Asp Ala Lys  413  1439 GCG GCC TAT GAA GCA GCT GTA GCA GCA AAT      ATT GCC GCA AAT GCA GCG 1486  414 Ala Ala Tyr Glu Ala Ala Val Ala Ala      Asn Asn Ala Ala Asn Ala Ala  429  1487 CTC ACA GCT GAA AAT ACT GCA ATT      AAG AAG CGC AAT GCG GAT GCT AAA 1534  430 Leu Thr Ala Glu Asn Thr Ala      Ile Lys Lys Arg Asn Ala Asp Ala Lys  445  1535 GCT GAT TAC GAA GCA AAA      CTT GCT AAG TAT CAA GCA GAT CTT GCC AAA 1582  446 Ala Asp Tyr Glu Ala      Lys Leu Ala Lys Tyr Gln Ala Asp Leu Ala Lys  461  1583 TAT CAA AAA GAT      TTA GCA GAC TAT CCA GTT AAG TTA AAG GCA TAC GAA 1630  462 Tyr Gln Lys      Asp Leu Ala Asp Tyr Pro Val Lys Leu Lys Ala Tyr Glu  477  1631 GAT GAA      CAA ACT TCT ATT AAA GCT GCA CTG GCA GAA CTT GAA AAA CAT 1678  478 Asp      Glu Gln Thr Ser Ile Lys Ala Ala Leu Ala Glu Leu Glu Lys His  493  1679      AAA AAT GAA GAC GGA AAC TTA ACA GAA CCA TCT GCT CAA AAT TTG GTC 1726      494 Lys Asn Glu Asp Gly Asn Leu Thr Glu Pro Ser Ala Gln Asn Leu Val  509       1727 TAT GAT CTT GAG CCA AAT GCG AAC TTA TCT TTG ACA ACA GAT GGG AAG      1774  510 Tyr Asp Leu Glu Pro Asn Ala Asn Leu Ser Leu Thr Thr Asp Gly      Lys  525  1775 TTC CTT AAG GCT TCT GCT GTG GAT GAT GCT TTT AGC AAA AGC      ACT TCA 1822  526 Phe Leu Lys Ala Ser Ala Val Asp Asp Ala Phe Ser Lys      Ser Thr Ser  541  1823 AAA GCA AAA TAT GAC CAA AAA ATT CTT CAA TTA GAT      GAT CTA GAT ATC 1870  542 Lys Ala Lys Tyr Asp Gln Lys Ile Leu Gln Leu      Asp Asp Leu Asp Ile  557  1871 ACT AAC TTA GAA CAA TCT AAT GAT GTT GCT      TCT TCT ATG GAG CTT TAT 1918  558 Thr Asn Leu Glu Gln Ser Asn Asp Val      Ala Ser Ser Met Glu Leu Tyr  573  1919 GGG AAT TTT GGT GAT AAA GCT GGC      TGG TCA ACG ACA GTA AGC AAT AAC 1966  574 Gly Asn Phe Gly Asp Lys Ala      Gly Trp Ser Thr Thr Val Ser Asn Asn  589  1967 TCA CAG GTT AAA TGG GGA      TCG GTA CTT TTA GAG CGC GGT CAA AGC GCA 2014  590 Ser Gln Val Lys Trp      Gly Ser Val Leu Leu Glu Arg Gly Gln Ser Ala  605  2015 ACA GCT ACA TAC      ACT AAC CTG CAG AAT TCT TAT TAC AAT GGT AAA AAG 2062  606 Thr Ala Thr      Tyr Thr Asn Leu Gln Asn Ser Tyr Tyr Asn Gly Lys Lys  621  2063 ATT TCT      AAA ATT GTC TAC AAG TAT ACA GTG GAC CCT AAG TCC AAG TTT 2110  622 Ile      Ser Lys Ile Val Tyr Lys Tyr Thr Val Asp Pro Lys Ser Lys Phe  637  2111      CAA GGT CAA AAG GTT TGG TTA GGT ATT TTT ACC GAT CCA ACT TTA GGT 2158      638 Gln Gly Gln Lys Val Trp Leu Gly Ile Phe Thr Asp Pro Thr Leu Gly  653       2159 GTT TTT GCT TCT GCT TAT ACA GGT CAA GTT GAA AAA AAC ACT TCT ATT      2206  654 Val Phe Ala Ser Ala Tyr Thr Gly Gln Val Glu Lys Asn Thr Ser      Ile  669  2207 TTT ATT AAA AAT GAA TTC ACT TTC TAT CAC GAA GAT GAA AAA      CCA ATT 2254  670 Phe Ile Lys Asn Glu Phe Thr Phe Try His Glu Asp Glu      Lys Pro Ile  685  2255 AAT TTT GAT AAT GCC CTT CTC TCA GTG ACT TCT CTT      AAC CGT GAA CAT 2302  686 Asn Phe Asp Asn Ala Leu Leu Ser Val Thr Ser      Leu Asn Arg Glu His  701  2303 AAC TCT ATT GAG ATG GCT AAA GAT TAT AGT      GGT AAA TTT GTC AAA ATC 2350  702 Asn Ser Ile Glu Met Ala Lys Asp Tyr      Ser Gly Lys Phe Val Lys Ile  717  2351 TCT GGT TCA TCT ATT GGT GAA AAG      AAT GGC ATG ATT TAT GCT ACA GAT 2398  718 Ser Gly Ser Ser Ile Gly Glu      Lys Asn Gly Met Ile Tyr Ala Thr Asp  733  2399 ACT CTT AAC TTT AAA CAG      GGT GAA GGT GGC TCT CGC TGG ACT ATG TAT 2446  734 Thr Leu Asn Phe Lys      Gln Gly Glu Gly Gly Ser Arg Trp Thr Met Tyr  749  2447 AAA AAT AGT CAA      GCT GGT TCA GGA TGG GAT AGT TCA GAT GCG CCG AAT 2494  750 Lys Asn Ser      Gln Ala Gly Ser Gly Trp Asp Ser Ser Asp Ala Pro Asn  765  2495 TCT TGG      TAT GGA GCA GGG GCT ATT AAA ATG TCT GGT CCG AAT AAC CAT 2542  766 Ser      Trp Tyr Gly Ala Gly Ala Ile Lys Met Ser Gly Pro Asn Asn His  781  2543      GTT ACT GTA GGA GCA ACT TCT GCA ACA AAT GTA ATG CCA GTT TCT GAC 2590      782 Val Thr Val Gly Ala Thr Ser Ala Thr Asn Val Met Pro Val Ser Asp  797       2591 ATG CCT GTT GTT CCT GGT AAG GAC AAT ACT GAT GGC AAA AAA CCA AAT      2638  798 Met Pro Val Val Pro Gly Lys Asp Asn Thr Asp Gly Lys Lys Pro      Asn  813  2639 ATT TGG TAT TCT TTA AAT GGT AAA ATC CGT GCG GTT AAT GTT      CCT AAA 2686  814 Ile Trp Tyr Ser Leu Asn Gly Lys Ile Arg Ala Val Asn      Val Pro Lys  829  2687 GTT ACT AAG GAA AAA CCC ACA CCT CCG GTT AAA CCA      ACA GCT CCA ACT 2734  830 Val Thr Lys Glu Lys Pro Thr Pro Pro Val Lys      Pro Thr Ala Pro Thr  845  2735 AAA CCA ACT TAT GAA ACA GAA AAG CCA TTA      AAA CCG GCA CCA GTA GCT 2782  846 Lys Pro Thr Tyr Glu Thr Glu Lys Pro      Leu Lys Pro Ala Pro Val Ala  861  2783 CCA AAT TAT GAA AAG GAG CCA ACA      CCG CCG ACA AGG ACA CCG GAT CAA 2830  862 Pro Asn Tyr Glu Lys Glu Pro      Thr Pro Pro Thr Arg Thr Pro Asp Gln  877  2831 GCA GAG CCA AAC AAA CCC      ACA CCG CCG ACC TAT GAA ACA GAA AAG CCG 2878  878 Ala Glu Pro Asn Lys      Pro Thr Pro Pro Thr Tyr Glu Thr Glu Lys Pro  893  2879 TTG GAG CCA GCA      CCT GTT GAG CCA AGC TAT GAA GCA GAG CCA ACA CCG 2926  894 Leu Glu Pro      Ala Pro Val Glu Pro Ser Tyr Glu Ala Glu Pro Thr Pro  909  2927 CCG ACA      AGG ACA CCG GAT CAG GCA GAG CCA AAT AAA CCC ACA CCG CCG 2974  910 Pro      Thr Arg Thr Pro Asp Gln Ala Glu Pro Asn Lys Pro Thr Pro Pro  925  2975      ACC TAT GAA ACA GAA AAG CCG TTG GAG CCA GCA CCT GTT GAG CCA AGC 3022      926 Thr Tyr Glu Thr Glu Lys Pro Leu Glu Pro Ala Pro Val Glu Pro Ser  941       3023 TAT GAA GCA GAG CCA ACG CCA CCG ACA CCA ACA CCA GAT CAA CCA GAA      3070  942 Tyr Glu Ala Glu Pro Thr Pro Pro Thr Pro Thr Pro Asp Gln Pro      Glu  957  3071 CCA AAC AAA CCT GTT GAG CCA ACT TAT GAG GTT ATT CCA ACA      CCG CCG 3118  958 Pro Asn Lys Pro Val Glu Pro Thr Tyr Glu Val Ile Pro      Thr Pro Pro  973  3119 ACT GAT CCT GTT TAT CAA GAT CTT CCA ACA CCT CCA      TCT GAT CCA ACT 3166  974 Thr Asp Pro Val Tyr Gln Asp Leu Pro Thr Pro      Pro Ser Asp Pro Thr  989  3167 GTT CAT TTC CAT TAC TTT AAA CTA GCT GTT      CAG CCG CAG GTT AAC AAA 3214  990 Val His Phe His Tyr Phe Lys Leu Ala      Val Gln Pro Gln Val Asn Lys 1005  3215 GAA ATT AGA AAC AAT AAC GAT ATT      AAT ATT GAC AGA ACT TTG GTG GCT 3262 1006 Glu Ile Arg Asn Asn Asn Asp      Ile Asn Ile Asp Arg Thr Leu Val Ala 1021  3263 AAA CAA TCT GTT GTT AAG      TTC CAG CTG AAG ACA GCA GAT CTC CCT GCT 3310 1022 Lys Gln Ser Val Val      Lys Phe Gln Leu Lys Thr Ala Asp Leu Pro Ala 1037  3311 GGA CGT GAT GAA      ACC ACT TCC TTT GTC TTG GTA GAT CCC CTG CCA TCT 3358 1038 Gly Arg Asp      Glu Thr Thr Ser Phe Val Leu Val Asp Pro Leu Pro Ser 1053  3359 GGT TAT      CAA TTT AAT CCT GAA GCT ACA AAA GCT GCA AGC CCT GGC TTT 3406 1054 Gly      Tyr Gln Phe Asn Pro Glu Ala Thr Lys Ala Ala Ser Pro Gly Phe 1069  3407      GAT GTC ACT TAT GAT AAT GCA ACT AAT ACA GTC ACC TTC AAG GCA ACT 3454      1070 Asp Val Thr Tyr Asp Asn Ala Thr Asn Thr Val Thr Phe Lys Ala Thr      1085  3455 GCA GCA ACT TTG GCT ACG TTT AAT GCT GAT TTG ACT AAG TCA GTG      GCA 3502 1086 Ala Ala Thr Leu Ala Thr Phe Asn Ala Asp Leu Thr Lys Ser      Val Ala 1101  3503 ACG ATT TAT CCA ACA GTG GTC GGA CAA GTT CTT AAT GAT      GGC GCA ACT 3550 1102 Thr Ile Tyr Pro Thr Val Val Gly Gln Val Leu Asn      Asp Gly Ala Thr 1117  3551 TAT AAG AAT AAT TTC ACG CTC ACA GTC AAT GAT      GCT TAT GGC ATT AAA 3598 1118 Tyr Lys Asn Asn Phe Thr Leu Thr Val Asn      Asp Ala Tyr Gly Ile Lys 1133  3599 TCC AAT GTT GTT CGG GTG ACA ACT CCT      GGT AAA CCA AAT GAT CCA GAT 3646 1134 Ser Asn Val Val Arg Val Thr Thr      Pro Gly Lys Pro Asn Asp Pro Asp 1149  3647 AAT CCA AAT AAT AAT TAT AAT      AAA CCA ACT AAG GTT AAT AAA AAC GAA 3694 1150 Asn Pro Asn Asn Asn Tyr      Ile Lys Pro Thr Lys Val Asn Lys Asn Glu 1165  3695 AAT GGC GTT GTT ATT      GAT GGT AAA ACA GTT CTT GCC GGT TCA ACG AAT 3742 1166 Asn Gly Val Val      Ile Asp Gly Lys Thr Val Leu Ala Gly Ser Thr Asn 1181  3743 TAT TAT GAG      CTA ACT TGG GAT TTG GAT CAA TAT AAA AAC GAC CGC TCT 3790 1182 Tyr Tyr      Glu Leu Thr Trp Asp Leu Asp Gln Tyr Lys Asn Asp Arg Ser 1197  3791 TCA      GCA GAT ACC ATT CAA AAA GGA TTT TAC TAT GTA GAT GAT TAT CCA 3838 1198      Ser Ala Asp Thr Ile Gln Lys Gly Phe Tyr Tyr Val Asp Asp Tyr Pro 1213      3839 GAA GAA GCG CTT GAA TTG CGT CAG GAT TTA GTG AAG ATT ACA GAT GCT      3886 1214 Glu Glu Ala Leu Glu Leu Arg Gln Asp Leu Val Lys Ile Thr Asp      Ala 1229  3887 AAT GGT AAT GAA GTT ACT GGT GTT AGT GTG GAT AAT TAT ACT      AAT CTT 3934 1230 Asn Gly Asn Glu Val Thr Gly Val Ser Val Asp Asn Tyr      Thr Asn Leu 1245  3935 GAA GCA GCC CCT CAA GAA ATT AGA GAT GTT CTT TCT      AAG GCA GGA ATT 3982 1246 Glu Ala Ala Pro Gln Glu Ile Arg Asp Val Leu      Ser Lys Ala Gly Ile 1261  3983 AGA CCT AAA GGT GCT TTC CAA ATT TTC CGT      GCC GAT AAT CCA AGA GAA 4030 1262 Arg Pro Lys Gly Ala Phe Gln Ile Phe      Arg Ala Asp Asn Pro Arg Glu 1277  4031 TTT TAT GAT ACT TAT GTC AAA ACT      GGA ATT GAT TTG AAG ATT GTA TCA 4078 1278 Phe Tyr Asp Thr Tyr Val Lys      Thr Gly Ile Asp Leu Lys Ile Val Ser 1293  4079 CCA ATG GTT GTT AAA AAA      CAA ATG GGA CAA ACA GGC GGC AGT TAT GAA 4126 1294 Pro Met Val Val Lys      Lys Gln Met Gly Gln Thr Gly Gly Ser Tyr Glu 1309  4127 AAT CAA GCT TAC      CAA ATT GAC TTT GGT AAT GGT TAT GCA TCA AAT ATC 4174 1310 Asn Gln Ala      Tyr Gln Ile Asp Phe Gly Asn Gly Tyr Ala Ser Asn Ile 1325  4175 GTT ATC      AAT AAT GTT CCT AAG ATT AAC CCT AAG AAA GAT GTG ACC TTA 4222 1326 Val      Ile Asn Asn Val Pro Lys Ile Asn Pro Lys Lys Asp Val Thr Leu 1341  4223      ACA CTT GAT CCG GCT GAT ACA AAT AAT GTT GAT GGT CAG ACT ATT CCA 4270      1342 Thr Leu Asp Pro Ala Asp Thr Asn Asn Val Asp Gly Gln Thr Ile Pro      1357  4271 CTT AAT ACA GTC TTT AAT TAC CGT TTG ATT GGT GGC ATT ATC CCT      GCA 4318 1358 Leu Asn Thr Val Phe Asn Tyr Arg Leu Ile Gly Gly Ile Ile      Pro Ala 1373  4319 AAT CAC TCA GAA GAA CTC TTT GAA TAC AAT TTC TAT GAT      GAT TAT GAT 4366 1374 Asn His Ser Glu Glu Leu Phe Glu Tyr Asn Phe Tyr      Asp Asp Tyr Asp 1389  4367 CAA ACA GGA GAT CAC TAT ACT GGT CAG TAT AAA      GTT TTT GCC AAG GTT 4414 1390 Gln Thr Gly Asp His Tyr Thr Gly Gln Try      Lys Val Phe Ala Lys Val 1405  4415 GAT ATC ACT CTT AAA AAC GGT GTT ATT      ATC AAG TCA GGT ACT GAG TTA 4462 1406 Asp Ile Thr Leu Lys Asn Gly Val      Ile Ile Lys Ser Gly Thr Glu Leu 1421  4463 ACT CAG TAT ACG ACA GCG GAA      GTT GAT ACC ACT AAA GGT GCT ATC ACA 4510 1422 Thr Gln Tyr Thr Thr Ala      Glu Val Asp Thr Thr Lys Gly Ala Ile Thr 1437  4511 ATT AAG TTC AAG GAA      GCC TTT CTG CGT TCT GTT TCA ATT GAT TCA GCC 4558 1438 Ile Lys Phe Lys      Glu Ala Phe Leu Arg Ser Val Ser Ile Asp Ser Ala 1453  4559 TTC CAA GCT      GAA AGT TAT ATC CAA ATG AAA CGT ATT GCG GTT GGT ACT 4606 1454 Phe Gln      Ala Glu Ser Tyr Ile Gln Met Lys Arg Ile Ala Val Gly Thr 1469  4607 TTT      GAA AAT ACC TAT ATT AAT ACT GTC AAT GGG GTA ACT TAC AGT TCA 4654 1470      Phe Glu Asn Thr Tyr Ile Asn Thr Val Asn Gly Val Thr Tyr Ser Ser 1485      4655 AAT ACA GTG AAA ACA ACT ACT CCT GAG GAT CCT GCA GAC CCT ACT GAT      4702 1486 Asn Thr Val Lys Thr Thr Thr Pro Glu Asp Pro Ala Asp Pro Thr      Asp 1501  4703 CCG CAA GAT CCA TCA TCA CCG CGG ACT TCA ACT GTA ATT ATC      TAC AAA 4750 1502 Pro Gln Asp Pro Ser Ser Pro Arg Thr Ser Thr Val Ile      Ile Tyr Lys 1517  4751 CCT CAA TCA ACT GCT TAT CAG CCA AGC TCT GTT CAA      GAA ACA TTA CCA 4798 1518 Pro Gln Ser Thr Ala Tyr Gln Pro Ser Ser Val      Gln Glu Thr Leu Pro 1533  4799 AAT ACG GGA GTA ACA AAC AAT GCT TAT ATG      CCT TTA CTT GGT ATT ATT 4846 1534 Asn Thr Gly Val Thr Asn Asn Ala Tyr      Met Pro Leu Leu Gly Ile Ile 1549  4847 GGC TTA GTT ACT AGT TTT AGT TTG      CTT GGT TTA AAG GCT AAG AAA GAT 4894 1550 Gly Leu Val Thr Ser Phe Ser      Leu Leu Gly Leu Lys Ala Lys Lys Asp 1565  4895 TGA CAG CAT AGA CAT TAC      ATT AGA ATT AAA AAG TGA GAT AGA AGC GAT 4942 1566 ***  4943 AAA TCA CAG      ATT GAG CTT TTA TCT CAT TTT TTG ATT AAT TAA AAG AGA 4990  4991 AAT AAC      TAG CCT ATC TTT GTT CTA TTA AAA AAA CAG TTA TGC TTA AAT 5038  5039 AGG      AAT ATC ATT AAC CAA TTT TAG CAA AAC GAT CAT TTA GTG TGA GTT 5086  5087      TTT AAC TAT CTT TCT TAA AGA AAA AAT GCT ATA ATA TTT TAG TTG CAC 5134      5135 ATT ACT AAC GTT TGA TAA GGT ACT TCG CAC TGC CTT

Since the strain GS-5 (K-3) of the present invention is obtained by integrating the pac gene into the chromosonal DNA of the strain GS-5, the leaving out of the pac gene from the strain is hardly caused and the strain extracellularly produces rPAc in high yield.

The site of the chromosomal DNA of the strain on which the pac gene exists can be confirmed by the Southern blot technique or the like. Therefore, rPAc can be obtained in high efficiency by isolating such a strain and culturing the same. Moreover, the processes for purifying rPAc can be substantially simplified since the content of rPAc in the culture supernatant is very high. The resulting rPAc can be used as a vaccine for dental caries in a variety of forms.

The strain GS-5 (K-3) of the present invention can be cultured, for instance, in the following manner. 37 g of a brain heart infusion medium is dissolved in 1l of distilled water, then the resulting solution is sterilized at 121° C. for 20 minutes and 1 ml of a 5 mg/ml erythromycin solution which has been filtered and sterilized in advance is added to and mixed with the foregoing solution to give a culture medium. The culture medium is dispensed in 10 ml portions into 24 ml sterilized test tubes, the strain GS-5 (K-3) is inoculated into each test tube and cultured at 37° C. for 18 hours to thus give a seed cultue liquid. 100 ml of the seed culture liquid is added to a 2l volume flask in which 1l of a culture medium having the same composition has been added and cultured at 37° C. for 18 hours to thus give a culture medium containing microorganisms. The medium is centrifuged at 10,000 X g for 15 minutes to obtain a culture supernatant.

The purification of rPAc from the culture supernatant can be performed by various means. For instance, there can be used gel filtration methods such as those in which dextrans or agaroses are employed as a stationary phase; ion-exchange techniques such as those in which AE, DEAE, QAE, CM, SP, Phospho or the like is used as an ion-exchange resin; hydrophobic chromatography techniques such as those in which Octyl Sepharose, Phenyl Sepharose or the like is employed as stationary phase; and affinity chromatography techniques.

The resultant vaccines for dental caries are administered, for instance, orally or via subcutaneous injection. The dose thereof desirably ranges from about 10 μg to about 50 mg and preferably 10 μg to 10 mg and the optimum dose thereof is 1 mg.

The bacteriological properties of the Streptococcus mutans GS-5 (K-3) (FERM BP-2437) are as follows. The determination of these bacteriological properties and the classification are performed according to the methods disclosed in Bergey's Manual of Systematic Bacteriology, 1986, 2.

A. Morphological Features

When the strain was cultured in a brain-heart infusion medium at 37° C. for 2 days, the following morphological features were observed:

1) Shape and Size of the Cell

It is a coccus; the size thereof ranges from 0.5 to 0.75 μm and it forms linkages.

2) Polymorphism: none.

3) Motility: none.

4) Spore: none.

5) Gram Staining: positive.

6) Resistance to Acid: negative.

B. Culturing Properties (Cultivability) 1) Brain heart infusion agar plate culture:

The strain grows at pH ranging from 7.0 to 7.4 and forms circular, flat, entire colonies. The surface of these colonies is smooth and glossy and the color thereof is yellowish white or pale brown.

2) Brain heart infusion agar slant culture:

It grows at pH ranging from 7.0 to 7.4 on wide belt-shaped regions and forms glossy yellowish white or pale brown colored colonies.

3) Brain heart infusion liquid culture:

It grows at pH ranging from 7.0 to 7.4, but does not form pellicles and the turbidity of the culture medium is uniform.

4) Broth gelatin stab culture:

The culture medium is not liquefied at all.

5) Litmus milk:

It grows sufficiently, produces acids and causes coagulation of milk.

C. Physiological Properties

1) Reduction of nitrates: negative.

2) Denitrification reaction: negative.

3) MP test: positive.

4) VP test: positive.

5) Production of indole: negative.

6) Formation of hydrogen sulfide: negative.

7) Hydrolysis of starches: negative.

8) Use of citric acid: It does not use citric acid in either Koser's or Christensen's mediums.

9) Use of inorganic nitrogen: It does not use either nitrates or ammonium salts.

10) Generation of dyes: negative.

11) Urease: negative.

12) Oxidase: negative.

13) Catalase: negative.

14) Range of growth conditions:

The growth temperature ranges from 33° to 38° C. (optimum temperature: 37° C.). The growth pH thereof ranges from 6.0 to 7. 4.

15) Behavior against oxygen: facultative anaerobic.

16) O-F test: positive.

17) Generation of acids and gases from sugars.: It produces acids from D-glucose, D-mannose, D-fructose, D-galactose, malt sugar (maltose), cane sugar (sucrose), trehalose, D-sorbit and D-mannit, but does not generate gases at all. It generates neither acids nor gases from L-arabinose, D-xylose, inosit, glycerin and starches.

D. Other Miscellaneous Characteristics

1) Decomposition of arginine: negative.

2) Hemolysis type: γ hemolysis.

3) Resistance to sodium chloride: resistant to 4% sodium chloride solution.

4) Other properties found necessary: It hydrolyzes esculin and is resistant to 2 U/ml of bacitracin. It generates acids from inulin, D-raffinose and D-melibiose. It synthesizes glucan from sucrose.

The aforesaid properties can be summarized as follows: the strain is a gram positive Streptococcus which produces acids from inulin, D-raffinose, D-melibiose and D-sorbit, which does not hydrolyze arginine and which is resistant to bacitracin. Thus, it can be concluded that the microorganism is a strain belonging to species Streptococcus mutans.

In the vaccine of the present invention, it is also possible to use the cortex of the cells of the foregoing S. mutans or those which are extracellularly produced by the strain in addition to the protein antigen (PAc) obtained by the method described above. More specifically, PAc is a protein present on the cortex of the cell bodies, but the strain secretes PAc extracellularly. Therefore, the easiest way for the preparation of the vaccine is to use the culture medium obtained after the cultivation of S. mutans. For instance, S. mutans strain ATCC 25175 is cultured in an outer solution obtained by dialyzing a brain-heart infusion culture medium (available from BBL Company, Difco Company etc.), the resulting culture supernatant is subjected to a salting out process carried out at a saturated ammonium sulfate concentrtion (60%), the product salted out is dissolved in a 50 mM Tris-hydrochloric acid buffer and then dialyzed against the same buffer. Subsequently, the preparation thus obtained is added to a column packed with DEAE Sephacel (available from Pharmacia Co., Ltd.) which has been equilibrated with the same buffer and elution is performed by a linear concentration gradient of NaCl ranging from 0 to 0.5 M whereby PAc is eluted at an NaCl concentration of about 0.2 M. The resulting PAc-containing fractions are pooled, concentrated and subjected to gel filtration using Sepharose CL-6B to obtain purified PAc-containing fractions which are used as the purified PAc.

Further, proteins equivalent to PAc and rPAc obtained from strains belonging to species Streptococcus mutans other than the S. mutans serotype c, which produce protein antigens common to PAc are also included in the scope of this invention and hence may be used in the vaccine composition of the present invention.

In the present invention, to the purified PAc there may optionaly be added carriers, diluents, or other additives such as preservatives, humectants, binders, adjuvants and agents for accelerating absorption to obtain pharmaceutical preparations used as nasal drops.

The amount of PAc to be added to the vaccine composition suitably ranges from 0.05 to 50 mg/0.2ml and preferably 0.5 to 20 mg/0.2 ml.

The vaccine composition of the present invention is preferably administered in an amount ranging from 0.05 to 0.6 m l/dose. Moreover, the vaccine composition of the present invention is suitably administered 2 or more times and preferably 2 to 6 times to achieve the desired immunization effect.

The vaccine composition of the present invention makes it possible to intranasally immunize a subject. Therefore, it may be easily administered even to many persons and the administration thereof is not accompanied by pain. Since at least two administrations are in general required for achieving the desired immunization effect, simplicity and the possibility of administration without pain are very important for the immunization procedures.

The antibody titer of the vaccine composition of the present invention can effectively be increased by the addition of cholera toxin B, a surfactant or a bile acid or a derivative thereof to the composition for nasal drops.

The amount of the cholera toxin B to be added to the composition suitably ranges from 10 μg to 20 mg/0.2 ml and preferably 50 μg to 10 mg/0.2 ml of the vaccine composition.

The surfactants may be anionic surfactants, cationic surfactants, nonionic surfactants and/or amphoteric surfactants, in particular cationic surfactants are preferred. These surfactants may be used alone or in any combination. The amount of the surfactants to be incorporated into the vaccine composition suitably ranges from 0.01 to 10% by weight, preferably 0.1 to 5% by weight on the basis of the total eight of the composition for anionic and nonionic surfactants and suitably ranges from 0.001 to 1.0% by weight and preferably 0.01 to 0.5% by weight on the basis of the total weight of the composition for cationic surfactants.

Examples of the anionic surfactants are carboxylic acid salts such as higher fatty acid salts (soaps) and N-acylamino acid salts of, for instance, lauroyl sarcosinate; sulfuric acid ester salts such as alkyl sulfates (for instance, lauryl sulfate), alkyl ether sulfates (for instance, polyoxyethylene alkyl ether sulfates) and fatty acid monoglyceride sulfates; alkane sulfonate; sulfosuccinates such as sodium dioctyl sulfosuccinate; N-acylsulfonates, fatty acid monoglyceride sulfonates and α-sulfofatty acid ester salts; alkyl phosphoric acid salts; and alkyl ether phosphoric acid salts.

Examples of the cationic surfactants are quaternary ammonium salts such as benzethonium chloride, benzalkonium chloride, cetyl pyridinium chloride, chlorohexyzine gluconate and chlorohexyzine. hydrochloride.

Examples of the nonionic surfactants are polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers (such as Triton X-100), polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters (such as Tween 20 and Tween 80), polyoxyethylene (hardened) castor oil, polyoxyethylene glycerin fatty acid esters and polyoxyethylene-polyoxypropylene copolymers.

Among the surfactants listed above, preferred are nonionic surfactants such as polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether and Triton X100, whose average molar number of added ethylene oxide ranges from 5 to 30; cationic surfactants such as benzethonium chloride and benzalkonium chloride; and anionic surfactants such as sodium lauryl sulfate and potassium lauryl sulfate.

Examples of bile acids usable in the present invention include etiobilianic acid, etioallobilianic acid, etianic acid, 3-hydroxy-nor-5α-cholanic acid, dehydrocholic acid, cilianic acid, 12-ketocholanic acid, lithocholic acid, deoxycholic acid, chenodeoxycholic acid, cholic acid and cholanic acid. In addition to these compounds, it is also possible to use derivatives and salts such as sodium and potassium salts thereof and sodium and potassium salts of the derivatives. Among these derivatives of bile acids, preferred are amide compounds of bile acids with amino acids or aminosulfonic acids and their sodium and potassium salts are also suitably employed in the present invention. Examples of such amino acids and aminosulfonic acids are glycine, serine, asparagine, aspartic acid and taurine. Among these, particularly preferred are sodium taurocholate, sodium glycocholate, sodium cholate and sodium deoxycholate.

The amount of these bile acids or the derivatives thereof to be incorporated into the vaccine composition of the present invention desirably ranges from 0.05 to 50 mg/0.2 ml and preferably 0.5 to 20 mg/0.2 ml.

The protective vaccine composition for dental caries of the present invention may further comprise an adjuvant such as alum, aluminum hydroxide, aluminum phosphate, aluminum sulfate and muramyl dipeptide; adjuvant fat-soluble components (agents for accelerating absorption) such as oleic acid, stearic acid and palmitic acid; humectants such as glycerin, sorbite, xylite, mannite, lactite, maltire and polyethylene glycols (such as PEG 400 and PEG 4,000); preservatives such as sorbic acid, chlorobutanol, benzoic acid, o-oxybenzoic acid ester, boric acid, dehydroacetic acid and thymol; and binders such as sodium polyacrylate, polyvinyl alcohol, polyvinyl pyrrolidone, sodium carboxy methyl cellulose, methyl cellulose, hydroxyethyl cellulose, carrageenan, sodium alginate, gum arabic, xanthane gum, montmorillonite, kaolin, hydrated silica, aluminum magnesium silicate and hectorite.

Alternatively, mammalian or birds are immunized with the protein antigen PAc of the present invention per se or a combination thereof with a surfactant and/or CTB to obtain antibodies and the resulting antibodies may be used in the protective vaccine composition for dental caries of the present invention as effective components.

According to the protective vaccine composition for dental caries, the antibody titer can effectively and simply be increased without pain by intranasally administering the protein antigen PAc.

In addition, the antibody titer of the vaccine composition of the present invention can more efficiently be increased if the protein antigen PAc is administered together with a surfactant, cholera toxin B or a bile acid or a derivative thereof.

Therefore, the present invention further includes two aspects, the one being a method for intranasally administering a vaccine composition for dental carries which comprises a protein antigen PAc and a carrier or a diluent and optionally a surfactant, cholera toxin B or a bile acid or a derivative thereof and the other being use of protein antigen PAc for the preparation of the vaccine composition for dental carries as nasal drops.

The present invention will hereunder be explained in more detail with reference to the following non-limitative Examples.

EXAMPLE 1 (1) Integration of the pac Gene into the Strain GS-5

The plasmid pPC77 carrying the pac gene of Streptcoccus mutans NCTC 10449 and a shuttle vector pSA3 were cleaved with restriction enzymes Bam HI and Sph I respectively. The cleaved pPC77 and pSA3 were linked with a T4 DNA ligase, the resultant plasmid was inserted into host cells, E. coli strain HB 101 (deposited with National Institute for Genetics under the accession number of ME 8568) by a transformation technique and a clone which was resistant to chloramphenicol and sensitive to ampicillin and tetracycline was selected. Recombinant plasmids were extracted from clones whose capacity of producing PAc had been confirmed by a colony immune blot technique or Western blot technique, the size thereof was determined by agarose electrophoresis and it was thus found that all the clones had the recombinant plasmid of 16.4 kb. One of these plasmids was named K and the plasmid K was inserted into a strain, S. mutans GS-5, incapable of producing PAc by an electroporation technique to transform the strain. The resulting PAc-producing strain was named GS-5 (K-X).

In the foregoing operations, a plurality of strains, GS-5 (K-X) were obtained, but their PAc-producing abilities differed from each other. Among these strains, the strains, GS-5 (K-3) having excellent PAc-prducing ability and GS-5 (K-9) which produced PAc, but whose PAc-producing ability was inferior to that of the former were examined on the sites at which the pac gene was inserted.

(2) Determination of the Site at Which pac Gene Was Integrated

The strains GS-5 and GS-5 (K-3) were lysed with lysozyme and the plasmids were separated from the chromosomal DNA's. The resulting fractions containing plasmid were analyzed by agarose electrophoresis and it was found that any plasmids were not present in the fractions thus obtained from the strains GS-5 and GS-5 (K-3) as shown in FIG. 1. On the other hand, the same procedures were repeated using the strain GS-5 (K-9) and it was found that the intended plasmid was present in the fraction thus obtained from the strain GS-5 (K-9).

The chromosomal-DNA was cleaved with Eco RI and then the resultant products were analyzed by the conventional Southern blot technique. When Sam HI fragments of the gene resistant to erythromycin were used as a probe, the chromosomal DNA's of the strains GS-5 and GS-5 (K-9) did not show any reactivity, while the fragment of about 16 kb of the chromosomal DNA of the strains GS-5 (K-3) exhibited reactivity therewith.

The foregoing results clearly show that, in the strain GS-5 (K-3), the plasmid pSM1 was integrated into the chromosomal DNA of the strain GS-5 as a result of homologous recombination. On the other hand, in the strain GS-5 (K-9) which can produce PAc, but whose PAc-producing ability is inferior to that of the strain GS-5 (K-3), it is found that the pac gene was present in the plasmid, but not in the chromosomal DNA thereof.

The Southern blot analysis is detailed in the article of E. M. Southern (1975) entitled "Detection of Specific Sequences Among DNA Fragments Separated by Gel Electrophoresis", J. Mol. Biol., 98, pp. 503-517.

(3) Cultivation and Purification of rPAc (Recombinant PAc)

The S. mutans strain GS-5 (K-3) was cultured in an external solution obtained by dialyzing TTY broth or BHI broth, the resulting culture supernatant was salted out at a saturated concentration of ammonium sulfate (60%), the products salted out were dissolved in 50 mM Tris-HCl buffer, dialyzed against the same buffer and the resulting dialyzate (preparation) was passed through a DEAE-cellulose column which had been equilibrated with the same buffer in advance. After passing the bed volume of the same buffer through the column two times, elution was performed at a linear concentration gradient of NaCl ranging from 0 to 0.5 mole. As a result, PAc was eluted at an NaCl concentration of about 0.2 mole. This eluted fraction as such can be used as a purified preparation of rPAc. When the strain GS-5 (K-B) is used, the purification processes can be substantially simplified as described above since the content of rPAc in the culture supernatant is very high.

The rPAc thus prepared can be used as vaccines for dental caries in various forms.

In the same manner used above, an NCTC 10449 strain, a GS-5 strain and a GS-5 (K-9) strain were likewise cultured, PAc secreted in the culture supernatants was purified, and the amount thereof (expressed in the reduced amount of the proteins contained) was determined by the Lowry method. The results are listed in the following Table I as relative values. As seen from these results, the GS-5 (K-B) strain of the present invention produces PAc in high yield.

                  TABLE I                                                          ______________________________________                                                              Relative Amount                                           Strain Used          of PAc Produced                                           ______________________________________                                         Streptococcus mutans NCTC 10449                                                                      1                                                        Streptococcus mutans GS-5                                                                            0                                                        Streptococcus mutans GS-5 (K-3)                                                                     48                                                        Streptococcus mutans GS-5 (K-9)                                                                     12                                                        ______________________________________                                    

(4) Immunization Test with rPAc

Compositions listed in the following Table II were dissolved in phosphate-buffered saline (PBS) and 0.1 ml each of the resulting solution was intraperitoneally injected twice in groups of mice (5 mice per group) at 10-days intervals to thus immunize the mice. 7 days after the second immunization, blood was sampled from the mice and the antibody titer against rPAc in blood was determined by the enzyme-linked immuno sorbent assay (ELISA method). The results obtained are summarized in Table II. In Table II, the antibody titer is expressed in the reciprocal of the highest rate of dilution at which the resulting serum showed reactivity in the ELISA method. In this respect, the serum was first diluted 10 times and thereafter it was diluted two times in order to determine the highest rate of dilution.

                  TABLE II                                                         ______________________________________                                         Group No.                                                                              Amount of rPAc (in 1 ml)                                                                        Antibody Titer in Blood                               ______________________________________                                         1       none (only PBS)  <10                                                   2       100 μg         980                                                  ______________________________________                                    

EXAMPLE 2

Groups of 5-week-old BALB/c mice (each comprising 5 animals) were immunized by intranasally administering 10 μl each of a solution containing PAc alone or a mixed solution containing PAc as well as a surfactant, cholera toxin B or a bile acid (salt) (the composition thereof is given below), three times at one-week intervals and further 4 weeks after the third immunization a fourth immunization was likewise performed. Then blood was sampled from each mouse and the antibody titer in blood was determined by the ELISA method. The results obtained are listed in the following Table III. In Table III, the antibody titer is expressed in the titer of the serum diluted 100 times, which was obtained 7 weeks after the final intranasal immunization.

    ______________________________________                                         Composition of the Mixed Solution (unit dose: 10 μl)                        Component            Amount                                                    ______________________________________                                         PAc (rPAc)           1 mg/ml                                                   Cholera toxin B      0.5 mg/ml                                                 Anionic surfactant   0.2% by weight                                            Cationic surfactant  0.2% by weight                                            Nonionic surfactant  0.2% by weight                                            Bile acid (salt)     0.2% by weight                                            ______________________________________                                    

                  TABLE III                                                        ______________________________________                                         Composition of the solution administered                                                               ELISA OD.sub.40 5                                      ______________________________________                                         PAc + cholera toxin B   0.55                                                   PAc + benzethonium chloride                                                                            0.52                                                   PAc + SDS*.sup.1        0.42                                                   PAc + Triton X-100*.sup.2                                                                              0.25                                                   PAc + glycolic acid     0.50                                                   PAc + sodium glycolate  0.52                                                   PAc alone               0.12                                                   ______________________________________                                          *.sup.1 SDS: sodium lauryl sulfate.                                            *.sup.2 Triton X100: polyoxyethylene alkyl phenyl ether.                 

EXAMPLE 3

The following exemplary preparations 1 to 13 of the protective vaccine composition for dental caries according to the present invention were prepared.

    ______________________________________                                         Preparation 1                                                                  Benzethonium chloride    0.1    g                                              Glycerin                 0.8    g                                              Hydroxyethyl cellulose   0.8    g                                              PAc                      0.25   g                                              Purified water           balance                                               total                    100    g                                              Preparation 2                                                                  Sodium lauryl sulfate    0.4    g                                              Xylite                   0.5    g                                              Hydroxymethyl cellulose  0.8    g                                              PAc                      0.25   g                                              Benzoic acid             0.1    g                                              Purified water           balance                                               total                    100    g                                              Preparation 3                                                                  Sucrose monopalmitic acid ester                                                                         1.2    g                                              sorbite                  0.6    g                                              Methyl cellulose         0.6    g                                              PAc                      0.4    g                                              Purified water           balance                                               total                    100    g                                              Preparation 4                                                                  Glycerin                 0.8    g                                              Hydroxyethyl cellulose   0.5    g                                              rPAc                     0.25   g                                              Cholera toxin B          0.08   g                                              Butyl Paraben HCl        0.1    g                                              Purified water           balance                                               total                    100     g                                             Preparation 5                                                                  Benzethonium chloride    0.1     g                                             Polyoxyethylene hardened castor oil                                                                     0.8     g                                             Xylite                   0.5     g                                             Hydroxymethyl cellulose  0.8     g                                             rPAc                     0.5     g                                             Benzoic acid             0.1     g                                             Alum                     0.02    g                                             Purified water           balance                                               total                    100     g                                             Preparation 6                                                                  Cetyl pyridinium chloride                                                                               1.5     g                                             Sorbite                  0.7     g                                             Gum arabic               0.3     g                                             rPAc                     0.5     g                                             Muramyl dipeptide        0.05    g                                             Purified water           balance                                               total                    100     g                                             Preparation 7                                                                  Glycerin monolauric acid ester                                                                          0.4     g                                             Polyoxyethylene sorbitan fatty acid ester                                                               0.5     g                                             Glycerin                 0.8     g                                             Hydroxymethyl cellulose  0.5     g                                             PAc                      0.25    g                                             Cholera toxin B          0.08    g                                             Purified water           balance                                               total                    100     g                                             Preparation 8                                                                  Glycerin                 0.8     g                                             Hydroxyethyl cellulose   0.5     g                                             PAc                      0.8     g                                             Butyl Paraben HC1        0.1     g                                             Stearic acid             0.05    g                                             Purified water           balance                                               total                    100     g                                             Preparation 9                                                                  Polyoxyethylene sorbitan stearic acid ester                                                             0.5     g                                             Glycerin                 0.8     g                                             Hydroxyethyl cellulose   0.5     g                                             PAc                      0.5     g                                             Cholera toxin B          0.08    g                                             Lauryl di(aminoethyl)glycine hydrochloride                                                              0.2     g                                             Purified water           balance                                               total                    100     g                                             Preparation 10                                                                 Chlorohexyzine gluconate 0.1     g                                             Sodium polyacrylate      0.2     g                                             rPAc                     0.25    g                                             Aluminum hydroxide       0.1     g                                             Oleic acid               0.5     g                                             Triton 100               0.8     g                                             Purified water           balance                                               total                    100     g                                             Preparation 11                                                                 Glycerin                 0.8     g                                             PAc                      0.08    g                                             Butyl Paraben hydrochloride                                                                             0.1     g                                             Sodium glycocholate      0.1     g                                             Stearic acid             0.05    g                                             Alum                     0.1     g                                             Purified water           balance                                               total                    100     g                                             Preparation 12                                                                 Sorbite                  2.0     g                                             rPAc                     0.05    g                                             Butyl Paraben hydrochloride                                                                             0.1     g                                             Cholic acid              0.2     g                                             Polyoxyethylene sorbitan fatty acid ether                                                               1.0     g                                             Purified water           balance                                               total                    100     g                                             Preparation 13                                                                 Glycerin                 2.0     g                                             rPAc                     0.08    g                                             Sodium glycocholate      0.1     g                                             Cholera toxin B          0.04    g                                             Purified water           balance                                               total                    100     g                                             ______________________________________                                     

What is claimed is:
 1. A method for preparing a vaccine against dental caries comprising integrating a protein antigen-expressing gene (Pac-expressing gene) into a Streptococcus mutans GS-5 strain to produce a variant bacterial strain; culturing the variant bacterial strain; the variant Streptococcus mutans GS-5 strain encoding a protein antigen to produce the protein antigen on the surface of cells of Streptococcus mutans or to extracellularly produce the protein antigen, wherein the protein antigen produced has a molecular weight ranging from about 170,000 to 220,000; and recovering the protein antigen produced by the variant bacterial strain.
 2. The method of claim 1 wherein the protein antigen has a molecular weight of about 190,000.
 3. The method of claim 1 wherein the Streptococcus mutans GS-5 strain is GERM BP-2436.
 4. The method of claim 1 wherein a Streptococcus mutans GS-5 (K-3) strain, FERM BP-2437, is cultured. 